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SubjectRe: [PATCH 5/7] Fix not good check of mem_cgroup_local_usage()
On Thu 16-06-11 12:54:43, KAMEZAWA Hiroyuki wrote:
> From fcfc6ee9847b0b2571cd6e9847572d7c70e1e2b2 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Date: Thu, 16 Jun 2011 09:23:54 +0900
> Subject: [PATCH 5/7] Fix not good check of mem_cgroup_local_usage()
>
> Now, mem_cgroup_local_usage(memcg) is used as hint for scanning memory
> cgroup hierarchy. If it returns true, the memcg has some reclaimable memory.
>
> But this function doesn't take care of
> - unevictable pages
> - anon pages on swapless system.
>
> This patch fixes the function to use LRU information.
> For NUMA, for avoid scanning, numa scan bitmap is used. If it's
> empty, some more precise check will be done.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
> mm/memcontrol.c | 43 +++++++++++++++++++++++++++++++++----------
> 1 files changed, 33 insertions(+), 10 deletions(-)
>
> Index: mmotm-0615/mm/memcontrol.c
> ===================================================================
> --- mmotm-0615.orig/mm/memcontrol.c
> +++ mmotm-0615/mm/memcontrol.c
> @@ -632,15 +632,6 @@ static long mem_cgroup_read_stat(struct
> return val;
> }
>
> -static long mem_cgroup_local_usage(struct mem_cgroup *mem)
> -{
> - long ret;
> -
> - ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
> - ret += mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
> - return ret;
> -}
> -
> static void mem_cgroup_swap_statistics(struct mem_cgroup *mem,
> bool charge)
> {
> @@ -1713,6 +1704,23 @@ static void mem_cgroup_numascan_init(str
> mutex_init(&mem->numascan_mutex);
> }
>
> +static bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
> +{
> + if (!nodes_empty(mem->scan_nodes))
> + return true;

How the non empty node mask guarantees that there is some reclaimable memory?

> + /* slow path */
> + if (mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_FILE))
> + return true;
> + if (mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_FILE))
> + return true;
> + if (noswap || !total_swap_pages)
> + return false;
> + if (mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON))
> + return true;
> + if (mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_ANON))
> + return true;
> + return false;
> +}
> #else
> int mem_cgroup_select_victim_node(struct mem_cgroup *mem)
> {
> @@ -1722,6 +1730,21 @@ static void mem_cgroup_numascan_init(str
> {
> return 0;
> }
> +
> +static bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
> +{
> + if (mem_cgroup_get_zonestat_node(mem, 0, LRU_INACTIVE_FILE))
> + return true;
> + if (mem_cgroup_get_zonestat_node(mem, 0, LRU_ACTIVE_FILE))
> + return true;
> + if (noswap || !total_swap_pages)
> + return false;
> + if (mem_cgroup_get_zonestat_node(mem, 0, LRU_INACTIVE_ANON))
> + return true;
> + if (mem_cgroup_get_zonestat_node(mem, 0, LRU_ACTIVE_ANON))
> + return true;
> + return false;
> +}
> #endif

Code duplication doesn't look good. What about a common helper?
>
>
> @@ -1811,7 +1834,7 @@ again:
>
> while (visit--) {
> victim = mem_cgroup_select_victim(root_mem);
> - if (!mem_cgroup_local_usage(victim)) {
> + if (!mem_cgroup_reclaimable(victim, noswap)) {
> /* this cgroup's local usage == 0 */
> css_put(&victim->css);
> continue;
>
> --
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--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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